When a semiconductor device such as a metal-oxide-semiconductor field-effect transistors (MOSFETs) is scaled down through various technology nodes, high k dielectric material and metal are adopted to form a gate stack. When forming such a device, the metal layer is tuned to have a proper work function to achieve the designed threshold voltage of the device. Currently, the threshold voltage (Vt) is controlled and engineered by tuning work function of entire gate region. The band edge work function is preferred to have good short channel control while tuning Vt (threshold voltage) by implanting impurities (dopants) into the device channel. However, both the short channel control and Vt target cannot be tuned independently and may not be met at the same time. Therefore, a structure and the method making the same are needed for additional freedom of tuning both the short channel effect and threshold voltage.